Another week, another fiddler.

Reveal solution by highlighting.

15 minutes. As shown in this spreadsheet.

Now, I have to admit, that’s a guess. It’s based on, fastest child carries slowest child some of the way, slowest child walks the rest of the way, meanwhile middle child was walking, fastest child goes back and then carries that child the rest of the way. A solution, where everybody arrives at the same time, will be optimal.

I can’t really argue, why it has to be that way. And it’s complicated to do something similar for the extra credit, 4 child version.